Modelling Plate for a Stereolithography Machine, Stereolithography Machine Using Said Modelling Plate and Tool for Cleaning Said Modelling Plate

ABSTRACT

The invention is a modelling plate ( 6; 6′; 6 ″) for a stereolithography machine ( 1 ) suited to produce three-dimensional objects (A) through superimposition of a plurality of layers (E) with predefined thickness of a liquid substance ( 3 ) that solidifies when subjected to a selective stimulation ( 4 ). The plate ( 6; 6′; 6 ″) comprises a work surface ( 7 ) that supports the object (A) and grooves ( 8 ) made in the work surface ( 7 ) along a development trajectory (X).

The present invention concerns a modelling plate for a stereolithographymachine, as well as a stereolithography machine comprising said plate.

The present invention also concerns a tool for cleaning the abovementioned modelling plate.

As is known, the stereolithography technique makes it possible toproduce three-dimensional objects by superimposing a succession oflayers obtained by means of a liquid resin that solidifies whensubjected to a predefined stimulation.

Each layer of the object is obtained by selectively stimulating theresin so as to solidify it in the points that make up a correspondingsection of the object to be is produced.

As is known, a stereolithography machine generally comprises a tanksuited to contain the liquid resin, a device suited to stimulate aliquid resin layer having a predefined thickness and a moving modellingplate that supports the three-dimensional object during its formation.

To create the first layer of the object, the surface of the plate isbrought to the level of the above mentioned liquid layer to bestimulated, so that the first layer of the object is formed against theplate and adheres to it.

To create each successive layer, the plate moves the object away fromthe previous position, so as to allow the resin to restore the liquidlayer that will serve to form the successive layer.

Then the plate moves the object back to such a position that the lastlayer is against the liquid resin layer, so that the latter solidifieswhile adhering to the previous layer.

The stereolithography machines of known type pose the drawback that itis not easy to remove the finished object from the modelling plate.

In particular, since the object adheres to the plate and is veryfragile, it must be detached using a sharp metal blade that is slidedover the plate to separate the object from the surface of the plateitself.

This operation involves the risk of deforming or breaking the object andtherefore it must be carried out manually and with great care, with thedouble drawback of increasing labour costs and the risk of rejects.

The blade poses another drawback lying in that some surface particlesare removed from the plate.

Besides damaging the plate, this causes another drawback, represented bythe fact that the above mentioned particles contaminate the residualliquid resin present in the tank, thus affecting the soundness of theobjects that are produced successively.

Further drawbacks are posed by the stereolithography machines in whichthe stimulation device is positioned under the tank, which is providedwith a bottom that is transparent to stimulation.

In this variant, the stimulation device is configured so as to solidifythe resin layer adjacent to the bottom of the tank itself, so that theobject is formed under the modelling plate and on creation of eachsuccessive layer the plate is progressively lifted from the bottom ofthe tank.

The vertical movements of the plate cause the resin to flow from thecentre of the plate towards its sides and vice versa, depending on thedirection of movement.

Due to the viscosity of the resin and its consequent difficulty inflowing, the movement of the plate exerts a certain pressure on thebottom of the tank, which increases in proportion to the viscosity ofthe resin, the plate movement speed and the proximity of the plate tothe bottom of the tank.

In particular, during the formation of the first layers, the modellingplate is arranged at a distance from the bottom of the tank in the orderof a few hundredths of a millimetre.

Therefore, during the formation of the first layers, the pressuresdetermined by the movements of the plate are so high that it isnecessary to limit the plate speed, with the inconvenience ofconsiderably increasing the processing costs. The problem describedabove is addressed in the Italian patent application VI2008A000311, inthe name of the same applicant who filed the present application.

This document discloses a stereolithography machine comprising a plateprovided with through holes that, allowing the resin to flow from oneface of the plate to the other, prevent the resin from flowing towardsthe sides of the plate. Therefore, advantageously, the presence of theholes reduces the amount of pressure exerted on the bottom of the tankand makes it possible to increase the plate movement speed even duringthe formation of the first layers.

Furthermore, the holes prevent the plate from adhering to the bottom ofthe tank, producing the so-called “sucker effect” described in detail inthe above mentioned document of the known art.

However, the holed plate poses the same drawbacks described above withreference to the removal of the object and to the cleaning of the plate,as well as adding new drawbacks.

It is known, in fact, that in order to make the layers adhere to thesurface of the plate it is necessary to stimulate a layer of resinslightly thicker than is strictly required.

Consequently, when a holed plate is used, part of the resin belonging tothe first layers of the object solidifies inside the holes and remainsstuck therein, thus hindering the successive removal of the plate at theend of the processing cycle.

In particular, if the object is removed by means of the above mentionedsharp metal blade, there is the inconvenience that the portions of resinthat solidified in the holes are separated from the rest of the objectand remain stuck in the holes.

Therefore, after removing the object, a further operation is necessaryto remove the resin that is stuck in the holes.

Differently from the variant embodiment described above, a furthervariant embodiment of a stereolithography machine has the stimulationdevice arranged over the tank and configured so as to solidify thesurface layer of the resin.

In this embodiment, the object is formed over the plate, which isprogressively lowered as the construction of the object proceeds.

Even if this variant embodiment does not pose the drawbacks related tothe pressure exerted on the bottom of the tank, it nevertheless posesthe drawbacks related to the removal of the object from the plate and tothe cleaning of the latter, described with reference to the previousvariant embodiment.

The present invention intends to overcome all the drawbacks of the knownart as outlined above.

In particular, it is a first object of the invention to provide amodelling plate for stereolithography machines that allows the finishedobject to be removed more comfortably than allowed by the plates ofknown type.

It is a further object of the invention to provide a plate that is easyto clean.

It is also the object of the invention to provide a plate that, whenused on a stereolithography machine provided with a stimulation devicearranged under the tank, facilitates the flow of the resin from thecentre of the plate towards its sides, and vice versa, compared to theplates of known type.

The objects described above are achieved by a modelling plate for astereolithography machine according to claim 1 and by astereolithography machine according to claim 9.

Further characteristics and details of the invention are described inthe corresponding dependent claims.

Advantageously, making it easier to remove the object from the platemeans reducing the need for labour and the number of rejects.

Furthermore, making it easier to clean the plate means reducing the riskof contaminating the resin and thus also means offering thecorresponding advantages.

Still advantageously, the easier flow of the resin allows plate movementspeeds to be adopted that are analogous to those achievable with holedplates of known type.

Therefore, it is possible to reduce the processing time of a singleobject and thus reduce its cost.

The said objects and advantages, together with others which will behighlighted below, are illustrated in the description of preferredembodiments of the invention which are provided by way of non-limitingexamples with reference to the attached drawings, wherein:

FIG. 1 shows an axonometric view of the stereolithography machine thatis the subject of the invention;

FIG. 2 shows a side section view of the machine shown in FIG. 1;

FIG. 2 a shows an enlarged detail of FIG. 2;

FIG. 3 shows an axonometric view of the modelling plate that is thesubject of the invention;

FIG. 4 shows a side section view of a detail of the plate shown in FIG.3;

FIGS. 4 a and 4 b show in detail a side section view of several variantembodiments of the plate shown in FIG. 4;

FIG. 5 shows an axonometric view of a tool for cleaning the plate of theinvention;

FIG. 6 shows a partial section view of the tool shown in FIG. 5;

FIG. 7 illustrates the use of the tool of FIG. 5 with the plate of FIG.3;

FIG. 8 shows a side section view of a detail of FIG. 7.

As shown in FIG. 1, the stereolithography machine 1 of the inventioncomprises a tank 2 suited to contain a liquid substance 3 suited tosolidify when subjected to a selective stimulation 4, shown in FIG. 2.

The above mentioned selective stimulation 4 is generated throughemission means 5 that convey it towards the tank 2.

Preferably but not necessarily the liquid substance 3 is alight-sensitive resin and the emission means 5 comprise a laser emitterassociated with scanner means 5 a of any known type suited to direct thelaser beam on the points of the layer of resin 3 to be solidified.

Obviously, variant embodiments of the invention may include other knowntypes of emission means 5, provided that they can solidify the liquidsubstance 3.

The machine 1 also comprises a modelling plate 6, provided with a worksurface 7 facing said emission means 5 and suited to support athree-dimensional object A being formed.

The machine 1 described above makes it possible to produce thethree-dimensional object A by superimposing a plurality of layers E ofsaid solidified resin 3 having a predefined thickness.

In particular, the first layers adhere to the work surface 7 of theplate 6, while the successive layers adhere to the previous ones.

Preferably but not necessarily the machine 1 is configured so as to formthe object A under the modelling plate 6, as shown in FIGS. 1 and 2.

In particular, the emission means 5 are arranged under the tank 2 thathas a bottom 2 a that is transparent to stimulation 4.

Obviously, in this case, the plate 6 is arranged with the work surface 7facing the bottom 2 a of the tank 2.

According to a variant embodiment of the stereolithography machine ofthe invention, not shown herein, the emission means 5 are arranged overthe tank 2.

In this second variant embodiment, the modelling plate 6 is arrangedwith the work surface 7 facing upwards and the three-dimensional objectA is formed over the plate.

The plate 6 comprises a plurality of grooves 8 made in the work surface7 along corresponding development trajectories parallel to one anotherand preferably rectilinear, as shown in FIG. 3.

During the formation of the first layers E of the object A adjacent tothe work surface 7 of the plate 6, the resin 3′ located in the grooves 8is not reached by the stimulation 4 and, therefore, remains liquid, thusdefining a corresponding number of channels interposed between thesolidified object A and the plate 6, as shown in FIG. 2 a.

At the end of the processing cycle, a corresponding elongated element 16belonging to a cleaning tool 14, shown in FIG. 5, can be inserted andslided into each one of the above mentioned channels.

The elongated element 16 can exert a thrusting action on thethree-dimensional object A in order to detach it from the work surface7, as shown in FIG. 8.

Therefore, the above mentioned grooves 8 make it easier to detach thefinished object A from the work surface 7, thus achieving one of theobjects of the invention.

Advantageously, the above mentioned thrusting action poses fewer risksof damaging the object A than the known techniques, according to whichthe object A is removed using a sharp, tool.

Furthermore, advantageously, the tool A is not provided with a cuttingedge and therefore cannot damage the plate 6.

Furthermore, as the object A is removed completely, it does not leavesolid residues inside the grooves 8, thus achieving the further objectto facilitate the cleaning of the plate 6.

The grooves 8 preferably extend to the perimeter edge of the worksurface 7, opening up at the level of the lateral surface of themodelling plate 6, as clearly visible in FIG. 3.

It is clear that the above mentioned open end allows the resin 3 to flowfrom the grooves 8 towards the lateral area of the plate 6, and viceversa, during the vertical movement of the plate 6 itself.

Preferably, both ends of the grooves 8 are open at the level of thelateral surface of the plate 6, advantageously allowing the resin 3 toflow in both directions.

Therefore, if the plate 6 is arranged with the work surface 7 facing thebottom 2 a of the tank 2, the resin 3 can flow along the grooves 8 fromthe centre of the plate 6 towards its sides, and vice versa.

Therefore, the invention achieves the object to facilitate the flow ofthe resin 3, especially when the plate 6 is arranged very near thebottom 2 a of the tank 2.

Advantageously, the facilitated flow of the resin 3 makes it possible toreduce the pressure exerted on the bottom 2 a of the tank 2 during thevertical movement of the plate 6.

Therefore, advantageously, it is possible to select movement speeds ofthe plate 6 that are equivalent to those possible, for example, withholed plates of known type, and in any case exceed those allowed byother known types of plate.

The grooves 8 preferably have depths 9 exceeding the thickness of the islayers E that make up the three-dimensional object A, for example in theorder of tenths of a millimetre or more.

Advantageously, this makes it possible to prevent the first layers ofthe object A from clogging the grooves 8, if solidification occurspartly inside them due to processing needs or mispositioning of theplate 6.

The first case is the most common and derives from the fact that, toensure the adhesion of the first layers E to the work surface 7 of theplate 6, a stimulation 4 is employed whose intensity is higher than theintensity strictly necessary to solidify the layer having predefinedthickness.

The higher intensity of the stimulation causes a partial solidificationof the resin 3′ arranged inside the grooves 8, as shown in FIG. 2 a.

The number of grooves 8, their width and their mutual distances on theplate 6 are parameters that can be selected by the manufacturer based onthe operating characteristics of the machine 1 on which the plate 6 mustbe used.

In general, a more viscous resin 3 will require more grooves 8 in orderto allow the optimal flow of the resin 3.

A higher number of grooves 8 also facilitates the removal of the objectA from the plate 6.

On the other hand, a reduced number of grooves 8 increases the surfacearea of the work surface 7, thus improving the adhesion of the object Aduring processing.

By way of example, it has been found that grooves 8 approximately onemillimetre wide arranged at a mutual distance of about one millimetrerepresent a good compromise in many circumstances.

It is evident, however, that in special cases it will be possible to useeven one groove 8 only.

The grooves 8 preferably develop with a uniform cross section 11 along arectilinear trajectory X.

In particular, and as shown in FIG. 4, the above mentioned cross section11 is rectangular.

According to a variant embodiment of the plate of the invention,indicated in FIG. 4 a by reference number 6′, the cross section 11′ hasan area 12 whose width exceeds the width 10 of the same section at thelevel of the work surface 7.

In other words, the cross section 11′ features an undercut surface that,advantageously, facilitates the adhesion of the three-dimensional objectA to the groove 8 during the processing cycle.

The undercut is small enough not to hinder the removal of the finishedthree-dimensional object A from the plate 6.

Preferably but not necessarily the above mentioned cross section 11 hasthe shape of a trapezium, with the long base defining the bottom 2 a ofthe groove 8 and the short base 10 corresponding to the opening of thegroove 8 on the work surface 7.

According to a further variant embodiment, indicated in FIG. 4 b byreference number 6″, the profile of the cross section 11″ features arecess 13 on one or both of the edges that delimit the cross section 11″laterally.

Advantageously, said recess 13 further improves the adhesion of thethree-dimensional object A to the plate 6 during the processing cycle.The depth of the above mentioned recess 13 is preferably limited to afew tenths of a millimetre, in such a way as not to hinder thesuccessive removal of the object A.

It is obvious that other variant embodiments may have thecharacteristics of the previous two embodiments, combined together.

The cleaning tool 14 shown in FIG. 5 comprises a supporting body 15 fromwhich one or more mutually parallel elongated elements 16 develop, eachone of which is configured so as to slide inside a corresponding groove8 of the plate 6.

The elongated elements 16 are arranged according to a reference plane Yand feature mutual distances that are the same as the mutual distancesbetween the corresponding grooves 8.

The sliding of the elongated elements 16 inside the correspondinggrooves 8 of the plate 6 makes it possible to exert a thrusting actionon the three-dimensional object A that, advantageously, causes it to beremoved from the work surface 7, as shown in FIGS. 7 and 8.

Preferably but not necessarily the tool 14 is provided with a number ofelongated elements 16 equal to the number of grooves 8 of the plate 6,in such a way as to allow the removal of the three-dimensional object Awith one pass only.

It is evident, however, that the tool 14 can be provided with any numberof elongated elements 16, even lower than the number of grooves 8.

As shown in FIG. 6, the width 17 of each elongated element 16 withrespect to a direction parallel to the reference plane Y is preferablyuniform and substantially equal to the width of the corresponding groove8 of the plate 6.

In this way, advantageously, each elongated element 16 has the maximumwidth compatible with the corresponding groove 8, thus allowing betterdistribution of the thrusting action on the three-dimensional object A.

The thickness 18 of the elongated elements 16 with respect to adirection orthogonal to the reference plane Y is preferably uniformalong the direction of development of the elongated elements 16.

Furthermore, the thickness 18 preferably does not exceed the depth 9 ofthe corresponding groove 8, so as to advantageously make it possible tocomfortably insert the elongated elements 16 between thethree-dimensional object A and the plate 6.

It is also preferable that the thickness 18 of the elongated elements 16be less than the depth 9 of the grooves 8, so as to facilitate thepenetration of the elongated elements 16 even when the resin 3solidifies partially inside the grooves 8, as described above.

According to a variant embodiment of the invention, not illustratedherein, the elongated elements 16 have increasing cross section from theend towards the supporting body 15, thus serving as wedges.

The elongated elements 16 preferably have rounded ends 16 a thatadvantageously facilitate their insertion in the corresponding grooves8, as shown in FIG. 8.

The elongated elements 16 are preferably made of a flexible material, inparticular a plastic material, with the advantage of allowing a moregradual force to be exerted on the object A during removal from theplate 6, so as to reduce the risk of damaging it.

The elongated elements 16 in plastic material offer a further advantagelying in that their hardness is lower than the hardness of the materialscommonly employed for the modelling plates, normally aluminium or othermaterials with similar hardness.

The reduced hardness of the elongated elements 16 prevents them fromremoving from the surface of the plate 6 some metal particles that maycontaminate the resin 3 during the successive processing cycles, andalso from damaging the plate 6.

The tool 14 can obviously be entirely made of a plastic material, withthe advantage of reducing costs.

For this purpose the depth 9 of the grooves 8 should preferably exceed0.5 mm, and preferably be in the order of 1 mm, so that the thickness ofthe tool 14 is compatible with the use of a plastic material.

It is also evident that, in variant embodiments of the invention, thetool 14 can be made of any material.

Obviously, the plate 6 and the tool 14 of the invention can be suppliedin a kit intended to be used in a stereolithography machine 1, whichincorporates the advantages of both components.

In practice, after the construction of the three-dimensional object Ahas been completed, it can be comfortably removed from the plate 6without damaging it, using the cleaning tool 14.

In particular, the ends 16 a of the elongated elements 16 are insertedin the corresponding grooves 8 of the plate 6 and are then slided alongthe grooves 8, as shown in FIG. 7.

During the sliding operation, the tool 14 is kept slightly inclined, soas to thrust the three-dimensional object A towards the outside of theplate 6 until it comes off.

Advantageously, as the three-dimensional object A is thrusted at thelevel of its base, it remains intact during separation from the plate 6,leaving no solid residue of resin 3 stuck in the grooves 8, as shown inFIG. 8.

Therefore, advantageously, the modelling plate 6 does not requirefurther cleaning operations before being used for the production of anew three-dimensional object.

The above clearly shows that the modelling plate and thestereolithography machine of the invention achieve all the set objects.

In particular, the grooved modelling plate makes it particularly easy toremove the finished object from the plate itself, especially if usingthe tool of the invention.

The use of the tool of the invention ensures an almost perfect cleaningof the modelling plate.

Furthermore, the grooves of the plate facilitate the flow of the resinduring the processing cycle, limiting the stress on the bottom of thetank and thus making it possible to increase the processing speed.

In any case, further variants of the invention, even if they are neitherdescribed herein nor illustrated in the drawings, must all be consideredprotected by the present patent, provided that they fall within thescope of the following claims.

Where technical features mentioned in any claim are followed byreference signs, those reference sings have been included for the solepurpose of increasing the intelligibility of the claims and accordinglysuch reference signs do not have any limiting effect on the protectionof each element identified by way of example by such reference signs.

1) Modelling plate (6; 6′; 6″) for a stereolithography machine (1)suited to produce three-dimensional objects (A) through superimpositionof a plurality of layers (E) with predefined thickness of a liquidsubstance (3) suited to solidify when subjected to a selectivestimulation (4), said plate (6; 6′; 6″) comprising a work surface (7)suited to support said object (A), characterized in that it comprises atleast one groove (8) made in said work surface (7) along a developmenttrajectory (X). 2) Plate (6; 6′; 6″) according to claim 1),characterized in that the depth (9) of said groove (8) exceeds thepredefined thickness of said layers (E). 3) Plate (6; 6′; 6″) accordingto claim 1) or 2), characterized in that said groove (8) extends to theperimeter edge of said work surface (7) so as to have at least one openend at the level of the lateral surface of said plate (6; 6′; 6″). 4)Plate (6; 6′; 6″) according to claim 3), characterized in that saidgroove (8) has both ends open at the level of said lateral surface ofsaid plate (6; 6′; 6″). 5) Plate (6; 6′; 6″) according to any of thepreceding claims, characterized in that said groove (8) has a uniformcross section (11, 11′, 11″) along said development trajectory (X). 6)Plate (6′) according to claim 5), characterized in that said crosssection (11′) has at least one area (12) whose width exceeds the width(10) of said cross section (11′) at the level of said work surface (7).7) Plate (6″) according to claim 5) or 6), characterized in that theprofile of said cross section (11″) has a recess (13) on at least one ofthe side edges of said cross section (11″). 8) Plate (6, 6′, 6″)according to any of the preceding claims, characterized in that itcomprises a plurality of said grooves (8) parallel to each other. 9)Stereolithography machine (1) for the production of three-dimensionalobjects, comprising: a tank (2) suited to contain a liquid substance (3)that solidifies when it is subjected to a selective stimulation (4);emission means (5) suited to generate said selective stimulation (4) andto convey it towards said tank (2), characterized in that it comprises amodelling plate (6; 6′; 6″) according to any of the claims from 1) to8). 10) Machine (1) according to claim 9), characterized in that saidplate (6; 6; 6″) is arranged with said work surface (7) facing thebottom (2 a) of said tank (2). 11) Machine (1) according to claim 9) or10), characterized in that it comprises a tool (14) for cleaning saidmodelling plate (6; 6′; 6″), comprising a supporting body (15) fromwhich at least one elongated element (16) develops, configured so thatit can slide inside a corresponding groove (8) of said plate (6; 6′;6″). 12) Machine (1) according to claim 11), characterized in that saidtool (14) comprises a supporting body (15) from which a plurality ofelongated elements (16) develop, each one of which is configured so thatit can slide inside a corresponding groove (8) of said plate (6; 6′;6″), said elongated elements (16) being mutually parallel and arrangedaccording to a reference plane (Y) at mutual distances that are the sameas the mutual distances between the corresponding grooves (8). 13)Machine (1) according to claim 11) or 12), characterized in that thewidth (17) of each one of said elongated elements (16) with respect to adirection parallel to said reference plane (Y) is substantially equal tothe width (10) of the corresponding groove (8) of said plate (6; 6′;6″). 14) Machine (1) according to any of the claims from 11) to 13),characterized in that the thickness (18) of each one of said elongatedelements (16) in a direction orthogonal to said reference plane (Y) doesnot exceed the depth (9) of the corresponding groove (8). 15) Machine(1) according to any of the claims from 11) to 14), characterized inthat said elongated elements (16) have rounded ends (16 a). 16) Machine(1) according to any of the claims from 11) to 15), characterized inthat said elongated elements (16) are flexible. 17) Machine (1)according to any of the claims from 11) to 16), characterized in thatthe hardness of said elongated elements (16) is lower than the hardnessof said plate (6; 6′; 6″).